Electronic devices including two or more parts or components require an electrical connection between at least two of the parts. While such electrical connections are well understood and dependably achieved, electrical connections between parts or components of miniaturized devices, such as those constructed by semiconductor fabrication techniques, require increasingly sophisticated techniques to electrically connect one part to another part. For the fabrication of MEMS devices, the electrical connection between parts becomes particularly critical since MEMS devices include both electrical and mechanical components having sizes of between 1 to 100 micrometers (i.e. 0.001 to 0.1 mm) where a completed MEMS device generally ranges in size from twenty (20) micrometers (20 millionths of a meter) to a millimeter (i.e. 0.02 to 1.0 mm).
In a MEMS device having distinct vertically oriented layers, typically composed of a substrate such as silicon, one or more local electrical contacts are formed between the two vertically oriented and distinct layers. Because the layers are separated, a connection is typically made between the two layers by depositing one or more metallic films on a surface of a first substrate which interfaces with a surface of a second substrate or a second vertical layer on the same substrate. The one or more metallic films are deposited on the substrates or devices and are patterned in order to provide locally conductive areas, electrically separated from each other.
The formation of the metallic films, which become conductors, involves several process steps, including the deposition of a first layer of metallic film, patterning the first layer, and then depositing additional layers and further patterning if required. Each layer which is to be connected requires its own conductor and consequently, the location of the conductors on each layer is critical to form a component or device. This multi-step process increases cost and requires a certain safety margin between two horizontally neighboring contacts.
In one type of conductor formation process, an anisotropic material is first deposited on a base substrate, such as silicon. This formation can be accomplished be using a lamination process by the deposition of a film. The material is then patterned if necessary. A second substrate is then placed in position over the base substrate and the two substrates are pressed together. In some instances, a small amount of heat is applied to cause the two interfacing substrates to adhere to one another.
Once the two substrates are mated, the two substrates are bonded by heating with temperatures that can be as high as 100° C., where the heat is applied for a relatively short period of time, on the order of one second or less. Temperatures, heat application times, and pressures applied vary depending on the type of substrates and the anisotropic materials being used.
In another type of conductor formation process, a first conductive layer is formed on a substrate followed by the deposition of an isolation material. The dielectric material is etched away in locations, where a connection is to be made. Then, a second conductive material is deposited and makes a connection to the first layer in the selected regions.
Consequently, there is a need for reducing the complexity of the processes used to form conductive layers on devices, components, and substrates.